Time- and dose-dependent post-irradiation changes of Fe3+- transferrin and Cu2+ -ceruloplasmin pools in blood, influence on ribonucleotide reductase activity in animal tissues and the effects of

2004 ◽  
pp. 338-373
Keyword(s):  
Ribonucleotide Reductase ◽  
Reductase Activity ◽  
Animal Tissues ◽  
Post Irradiation ◽  
Dose Dependent ◽  
Ribonucleotide Reductase Activity

Temperature-sensitive DNA mutant of Chinese hamster ovary cells with a thermolabile ribonucleotide reductase activity

1990 ◽  
Vol 10 (11) ◽  
pp. 5688-5699
Author(s):  
B E Wojcik ◽  
J J Dermody ◽  
H L Ozer ◽  
B Mun ◽  
C K Mathews
Keyword(s):  
Dna Synthesis ◽  
Ribonucleotide Reductase ◽  
Chinese Hamster Ovary ◽  
Reductase Activity ◽  
Chinese Hamster ◽  
Temperature Shift ◽  
Ovary Cell ◽  
Temperature Sensitive ◽  
Dntp Pool ◽  
Ribonucleotide Reductase Activity

JB3-B is a Chinese hamster ovary cell mutant previously shown to be temperature sensitive for DNA replication (J. J. Dermody, B. E. Wojcik, H. Du, and H. L. Ozer, Mol. Cell. Biol. 6:4594-4601, 1986). It was chosen for detailed study because of its novel property of inhibiting both polyomavirus and adenovirus DNA synthesis in a temperature-dependent manner. Pulse-labeling studies demonstrated a defect in the rate of adenovirus DNA synthesis. Measurement of deoxyribonucleoside triphosphate (dNTP) pools as a function of time after shift of uninfected cultures from 33 to 39 degrees C revealed that all four dNTP pools declined at similar rates in extracts prepared either from whole cells or from rapidly isolated nuclei. Ribonucleoside triphosphate pools were unaffected by a temperature shift, ruling out the possibility that the mutation affects nucleoside diphosphokinase. However, ribonucleotide reductase activity, as measured in extracts, declined after cell cultures underwent a temperature shift, in parallel with the decline in dNTP pool sizes. Moreover, the activity of cell extracts was thermolabile in vitro, consistent with the model that the JB3-B mutation affects the structural gene for one of the ribonucleotide reductase subunits. The kinetics of dNTP pool size changes after temperature shift are quite distinct from those reported after inhibition of ribonucleotide reductase with hydroxyurea. An indirect effect on ribonucleotide reductase activity in JB3-B has not been excluded since human sequences other than those encoding the enzyme subunits can correct the temperature-sensitive growth defect in the mutant.

Alterations in the components of ribonucleotide reductase in hydroxyurea-resistant hamster cells

1983 ◽  
Vol 3 (8) ◽  
pp. 741-748 ◽  
Author(s):  
Jim A. Wright ◽  
Joseph G. Cory
Keyword(s):  
Ribonucleotide Reductase ◽  
Reductase Activity ◽  
Antitumor Agent ◽  
Resistant Cell ◽  
Resistant Cell Line ◽  
Wild Type ◽  
Type Analysis ◽  
Similar Mode ◽  
Ribonucleotide Reductase Activity ◽  
Effector Binding

Two components of mammalian ribonucleotide reductase have been separated by blue dextran-Sepharose chromatography from a hydroxyurea-resistant cell line, NcR-30A2, and its parental wild type. Analysis of reductase activity in these cells and the enzyme components reveals that there are three alterations involving ribonucleotide reductase activity in NcR-30A2 cells. There is an elevation in the effector-binding (EB) component, an elevation in the non-heine-ironcontaining (NHI) component, and an alteration in the NHI component that renders the enzyme less sensitive to inhibition by hydroxyurea. These findings easily account for the resistance of NcR-30A2 cells to the antitumor agent hydroxyurea, and to other drugs with a similar mode of action.

Sign in / Sign up

Export Citation Format

Share Document